1. Field of the Invention
The present invention relates to sliding rotation members for highly reliable continuously variable transmission (CVT) for use in a toroidal CVT, such as a disk and power roller bearing, and an evaluation method of the members.
2. Description of the Related Art
For an input/output disk and power roller bearing for use in a toroidal continuously variable transmission (CVT), whose use environments include a high load and high surface pressure and which are positioned with important protective components, there have been proposed a large number of techniques for enhancement of durability in order to prevent breakage and flaking in a short time. For example, in Jpn. Pat. Appln. KOKAI Publication No. 2001-032900 (hereinafter referred to as Prior Document 1), there are disclosed chemical components of alloy steels for use in the input/output disk and power roller bearing, and a carbon amount, nitrogen amount, surface hardness, and the like of a function surface are limited, and preferable alloy components, heat treatment quality, and the like for enhancing the durability.
Moreover, in Jpn. Pat. Appln. KOKAI Publication No. 2001-026840 (hereinafter referred to as Prior Document 2), it is disclosed that a high-cleanliness steel is used in order to prevent breakage and flaking from being generated starting at a large nonmetal inclusion in a steel in a short time. Furthermore, a method of performing an ultrasonic flaw detection/inspection is used to guarantee that the large nonmetal inclusions do not exist in a traction surface 62 and surface layer portion of the input/output disk shown in FIG. 9, and a traction surface 67 and surface layer portion of an inner ring of the power roller bearing shown in FIG. 10. For example, it is guaranteed that the nonmetal inclusion having a maximum size of 0.1 mm or more does not exist within 0.5 mm from the surface in a disclosed member for CVT.
Moreover, for the use environments of a toroidal continuously variable transmission disk and power roller, high torque transmission capabilities are required from properties described later as compared with other types of continuously variable transmissions. It is necessary to apply a highly durable material which is not broken by a very large bend stress and repeated stress. To solve the problem, the present inventors have developed and proposed a management method of a steel which satisfies durability necessary especially for the CVT disk and power roller in Jpn. Pat. Appln. KOKAI Publication No. 11-193855 (hereinafter referred to as Prior Document 3).
To detect an inner defect of a steel material for use as a material of a bearing ring, only a defect inspection has heretofore been performed by an ultrasonic inspection in a steel manufacturing process. The ultrasonic inspection comprises: transmitting an ultrasonic wave to the inside of a rolled steel material from an outer peripheral surface thereof in water or on a base to detect a flaw. For example, a normal wave method described in xe2x80x9cpage 31, No. 6, Vol. 46, Tokushuko, Tokushuko Club Associationxe2x80x9d (hereinafter referred to as Prior Document 4), and the like are known.
In the inspection of defects (nonmetal inclusions) of the steel material in a steel maker, only large defects each having a width of several hundreds of micrometers and a length of several millimeters or more are detected because of the properties of the inspection. Additionally, a representative inspection (sampling inspection) is performed so that the high-cleanliness steel is entirely managed. However, the presence/absence of harmful inclusions has not been grasped or guaranteed with respect to all the steel materials (total inspection) in the existing technique.
Moreover, in recent years, it has been possible to detect even the nonmetal inclusion, for example, having a micro size of about 0.01 mm (10 xcexcm) using a high frequency in the ultrasonic inspection in a background of progress of a nondestructive inspection technique. However, in the ultrasonic inspection, when the frequency is increased, attenuation of the ultrasonic wave inside the steel material increases, and the method is not practical. Especially when the surface of the steel material becomes rough, the attenuation of the ultrasonic wave further increases. Therefore, for a practical range of the size of the inclusion, in which the total inspection of a product is possible, only a large defect having a width of several hundreds of micrometers and a length of several millimeters or more is detected in the existing circumstances.
The toroidal continuously variable transmission (CVT) disk and power roller bearing member having large defects inside (particularly in the vicinities of surfaces) are sometimes broken in a relatively short time, when repeatedly undergoing bend stresses. Particularly a rolling member of the large CVT repeatedly undergoes a high bend stress, and therefore tends to flaking or crack starting at a position deeper than a maximum stress generated position in which a conventional general-purpose rolling bearing has heretofore undergone the stress. Concretely, in input/output disks 31, 32 of the large CVT, a large repeated bend stress is added to portions (traction surface 62 and surface layer portion) shown by diagonal lines in FIG. 11, and a high tensile stress is generated. Moreover, in the inner ring of the power roller bearing of the large CVT, the large repeated bend stress is added to portions (traction surface 67, inner peripheral surface 68, rolling surface 69, and surface layer portion) shown by the diagonal lines in FIG. 12, and the high tensile stress is generated. Therefore, the flaking or cracks are easily generated starting at these surfaces 62, 67, 68, 69 and surface layer portions.
Additionally, in Prior Document 1 described above, it is proposed that the alloy components are optimized and heat treatment quality is specified in order to prevent the generation of the flaking or cracks. Moreover, in the invention of Prior Document 1, the traction surfaces 62 and surface layer portions of the input/output disks 31, 32 shown in FIG. 11 are strengthened, and the traction surfaces 67, inner peripheral surfaces 68, rolling surfaces 69, and surface layer portions of power roller inner rings 36a, 37a shown in FIG. 12 are strengthened, so that the entire strength is enhanced. However, it is not proposed to improve the large inclusion at which the flaking or crack starts.
Moreover, in Prior Document 2 described above, it is proposed that among the traction surfaces 62, inner peripheral surfaces 63, and surface layer portions of the input/output disks 31, 32 shown in FIG. 11, and the traction surfaces 67, inner peripheral surfaces 68, and rolling surfaces 69 of the power roller inner rings 36a, 37a shown in FIG. 12, particularly the large inclusions of the surface layer portions corresponding to the traction surfaces 62, 67 are detected and guaranteed in order to prevent the breakage or the flaking in the short time. However, in the invention of Prior Document 2, only the surface layer portions of the traction surfaces 62, 67 are objects of a precision inspection (or the total inspection), but the surface layer portions of the surfaces 63, 68, 69 other than the traction surfaces are not the objects of the precision inspection (or the total inspection).
A future demand for the CVT lies not only in long life and breakage prevention of the disk and power roller but also in eradication of accidental generation of a short-life bearing. This is a demand for a highly reliable member for the CVT which has no possibility of generation of short-life components even under conditions further stricter than before, with future elongation of guarantee period of a car.
The present invention has been developed to solve the above-described problems, and an object thereof is to provide a long-life sliding rotation member for CVT in which flaking is not easily generated in a sliding surface, and an evaluation method of a highly reliable sliding rotation member for CVT in which it is possible to detect all defects (particularly, nonmetal inclusions) existing particularly in a surface layer portion of an inner-diameter end in which a stress rises during operation of a CVT constituting member with a high precision.
One of characteristics of a toroidal CVT is that the CVT can bear a larger input torque than other CVTs (e.g., a belt CVT) can. With a car of a large engine displacement as an object in which a large torque is generated, the toroidal CVT receives a larger input torque. The toroidal CVT is of a type such that a large load can be received as compared with the belt CVT, and therefore a higher load and surface pressure are applied to a disk and power roller. In the future it is expected that a portion undergoing a repeated bend fatigue is positioned more deeply in the toroidal CVT.
In Prior Document 2, the present inventors have proposed that the nonmetal inclusion existing within 0.5 mm right under the traction surface and having a maximum diameter of 0.1 mm or more is limited and this can prevent the member from breaking. That is, as a result of intensive researches, the present inventors have found that the nonmetal inclusion (defect) existing within 0.5 mm from the traction surface and having a maximum diameter of 0.1 mm or more is a start point of bend fatigue destruction of a CVT component, and have proposed concrete solution means in Prior Document 2 based on the finding.
However, as a result of the subsequent research, it has been found that the bend fatigue destruction (hereinafter referred to simply as xe2x80x9cbreakagexe2x80x9d) is generated with a stricter use condition of the toroidal CVT component even in a position of the nonmetal inclusion deeper than the position described in Prior Document 2 described above. That is, as a result of the research under a stress condition stricter than a conventional condition, the present inventors have found that the breakage is sometimes generated even in a position deeper than the depth disclosed in Prior Document 2 and that the breakage is sometimes generated even in a defect smaller than the defect with the size disclosed in Document 2.
Then, the present inventors have intensively researched a relation between the input torque and breakage and the size of the nonmetal inclusion. As a result, it has been found that the defect having a square root length of 0.1 mm or more (more preferably 0.05 mm or more) is prevented from existing in a region within twice a depth of a position (Z0) of maximum shear stress undergone by the toroidal CVT component, and this can prevent the toroidal CVT component from breaking.
Moreover, the sliding surface undergoes rolling fatigue between the disk and power roller. When the large nonmetal inclusion exists right under the sliding surface, there is a problem that the flaking is generated with the short life. When the toroidal CVT component flaking, a trouble is generated in the running of a car. Therefore, it is important to lengthen the life against the rolling fatigue and eradicate short-life components. In order to solve the problems, as a result of the intensive research of the relation between the input torque and flaking and the size of the nonmetal inclusion, the present inventors have found that the elimination of the nonmetal inclusion having a square root length of 0.05 mm or more within twice the depth (Z0) of maximum shear stress undergone by the toroidal CVT component can prevent the component from peeling in a short time.
On the other hand, the present inventors have noted the ultrasonic inspection as a method of evaluating the nonmetal inclusion existing under the sliding surface of the disk and power roller bearing of the CVT, and have made intensive efforts in the improvement of the inspection method. As a result, it has been found that it is possible to detect the nonmetal inclusion of 0.1 mm or less existing within 0.5 mm from the surface with application of an angle wave method (surface wave method), and this has been disclosed in Prior Document 2 described above. However, a main object of the invention disclosed in Prior Document 2 is to detect the defect in a relatively shallow position within 0.5 mm from the surface. Therefore, with twice the depth (Z0) of the present invention, for example, a depth of 2 mm to 3 mm is an object depending on the size of the input torque. Therefore, it is necessary to also detect the defects (including the nonmetal inclusion, macro-streak flaw, and open crack) each having a square root length of 0.05 mm or more or 0.1 mm or more in a position of a depth six times a conventional object depth.
Prior Document 2 described above discloses a method of detecting the defect in the depth of 0.5 mm under the surface. Furthermore, the present inventors have intensively researched the ultrasonic inspection in which the portion having a depth of 0.5 mm or more under the surface can be inspected with a high precision, and have completed the present invention.
According to the present invention, there is provided a toroidal continuously variable transmission comprising: an input disk disposed on an input shaft; an output disk disposed on an output shaft; and a power roller bearing which includes an inner ring, an outer ring and a plurality of rolling members, in which the inner ring is rollingly contacted in the input disk and output disk and which transmits a power of the input shaft to the output shaft, wherein a maximum shear stress depth obtained on a condition on which the input disk is rolling contacted in the inner ring of the power roller bearing in a maximum deceleration state of the toroidal continuously variable transmission and the power is transmitted is defined as a symbol Zo, a size of a defect obtained in accordance with a shape of the defect detected by a nondestructive inspection method is defined as a square root length, and then at least one of the input disk and the inner ring of the power roller bearing does not include a defect of 0.05 mm or more in terms of the square root length in a range of a depth from a traction surface which is twice the above-described Zo.
According to the present invention, there is provided a sliding rotation member for a toroidal continuously variable transmission, which is rotatably supported by a support shaft in the toroidal continuously variable transmission, and slides on another member, wherein a maximum shear stress depth generated at a maximum deceleration time of the toroidal continuously variable transmission is defined as Z0, a size of a defect obtained in accordance with a shape of the defect detected by a nondestructive inspection method is defined as a square root length, and then a defect of 0.05 mm or more in terms of the square root length is not included in a range of a depth from the surface of the sliding rotation member which is twice the above-described Z0.
The defect includes a nonmetal inclusion, macro-streak flaw, and opening crack. Since most of the defects detected from CVT components are the nonmetal inclusions, it is essential to prevent large nonmetal inclusions from existing in portions shown by diagonal lines in FIGS. 7, 8. In general, the large nonmetal inclusion has a maximum diameter of 0.05 mm or more, and there are nonmetal inclusions having various shapes. Therefore, the size of the defect is defined by the square root length entirely in the present invention.
Here, the xe2x80x9csquare root lengthxe2x80x9d is obtained in the following 1) and 2) in accordance with the shape of the defect.
1) When the shape of the defect is linear (linear defect), a square root (Lxc3x97D)xc2xd of a product of length L and width D of the defect is defined as the square root length.
2) When the shape of the defect is granular, spherical, or clumpy (nonlinear defect), a square root (D1xc3x97D2)xc2xd of a product of maximum diameter (long-axis diameter) D1 and minimum diameter (short-axis diameter) D2 of the defect is defined as the square root length.
According to a first aspect of the present invention, when the surface of the sliding rotation member (the input disk, the inner ring of the power roller bearing) is a rolling contact surface (traction surface), the defect existing in the range of the depth from the rolling contact surface (traction surface) twice the maximum shear stress depth Z0 is an object. The defect is detected using a combination of a surface wave method, angle wave method, and normal wave method, acceptance/rejection is judged based on the detected result, and a defect of 0.10 mm or more in terms of the square root length is prevented from being included in the portion of the depth range (claim 1). In this case, it is more preferable on quality assurance to prevent the defect of 0.05 mm or more (particularly the nonmetal inclusion) from being included (claim 2).
Moreover, when the another member is the inner ring of the power roller bearing, that is, when the sliding rotation member is the input disk or the output disk, as shown in FIG. 7, it is preferable not to include a defect exceeding 0.20 mm in terms of the square root length (particularly the nonmetal inclusion) in a portion in at least a half depth Ll of a diametric length of an end surface on an inner peripheral surface side and in at least one-third depth C/3 of an axial length of the inner peripheral surface from an end surface side (claim 3).
Furthermore, the another member is an input or output disk, that is, the sliding rotation member is a power roller bearing inner ring. In this case, as shown in FIG. 8, it is preferable not to include a defect exceeding 0.20 mm in terms of a square root length (particularly the nonmetal inclusion) in a portion in a depth L2 which is at least a half of a diametric length of the end surface from an inner peripheral surface side and in a depth F/2 which is at least a half of the axial length of the inner peripheral surface from an end surface side (claim 4).
According to the present invention, there is provided an evaluation method of a sliding rotation member for a toroidal continuously variable transmission, comprising: immersing the sliding rotation member rotatably supported by a support shaft in the toroidal continuously variable transmission and slid on another member during use together with an ultrasonic probe into a transmission medium; allowing an ultrasonic wave to be incident upon the sliding rotation member from the ultrasonic probe via the transmission medium; and evaluating defects existing in the surface and an inner portion of the sliding rotation member based on a waveform of ultrasonic echo reflected from the sliding rotation member, the method comprising:
(a) a step of using at least one of a surface wave method and angle wave method to scan the surface of the sliding rotation member and a portion right under the surface;
(b) a step of defining a maximum shear stress depth generated inside the sliding rotation member at a maximum deceleration time of the toroidal continuously variable transmission as depth Z0, and using at least one of the angle wave method and a normal wave method to scan a portion of a depth from the surface which is twice the maximum shear stress depth Z0; and
(c) a step of defining a size of the defect obtained in accordance with a shape of the defect as a square root length, judging the sliding rotation member to be rejected, when the square root length of the defect detected by the steps (a) and (b) is 0.10 mm or more (preferably 0.05 mm or more), and judging the sliding rotation member to be accepted, when the square root length of the defect detected by the steps (a) and (b) is less than 0.10 mm (preferably less than 0.05 mm).
The surface (incidence surface) upon which the ultrasonic wave is incident is a traction surface or end surface of the sliding rotation member. The traction surface is a surface which undergoes a dynamic repeated stress by a mutual sliding contact with the other members.
When the sliding rotation member is the input or output disk, the ultrasonic wave is transmitted into the sliding rotation member from the end surface (claim 5). The end surface is positioned between the inner peripheral surface brought into contact with or disposed opposite to the support shaft and the traction surface, and substantially crosses at right angles to the support shaft. As shown in FIGS. 15 and 16, ultrasonic waves 4 are transmitted into a portion in a half (L1) of the diametric length W of an end surface 70 from an inner peripheral surface 63 side and a depth C/3 which is at least ⅓ of the axial length of the inner peripheral surface 63 from an end surface 70 side, and a surface layer portion right under the end surface 70 and inner peripheral surface 63 is scanned.
Also when the sliding rotation member is the inner ring of the power roller bearing, the ultrasonic wave is transmitted into the sliding rotation member from the end surface (claim 6). The end surface is in a position defined by the inner peripheral surface brought into contact with or disposed opposite to a pivot shaft 50, pivot shaft, and rolling groove, and substantially crosses at right angles to the pivot shaft. As shown in FIGS. 17 and 18, the ultrasonic waves 4 are transmitted into a portion in a half (L2) of a diametric length G of an end surface 75 from an inner peripheral surface 68 side and a depth F/2 which is at least a half of the axial length of the inner peripheral surface 68 from an end surface 75 side, and the surface layer portion right under the end surface 75 and inner peripheral surface 68 is scanned.
In this case, it is preferable to use an ultrasonic wave with a predetermined frequency in a range of 5 MHz to 30 MHz in the steps (a) and (b). It is further preferable to use an ultrasonic wave with the predetermined frequency in a range of 5 MHz to 15 MHz in the step (a) and to use an ultrasonic wave with the predetermined frequency in a range of 10 MHz to 25 MHz in the step (b).
In a concrete example, the angle wave method or the surface wave method is used in inspecting the depth of 0.5 mm from the surface, and the defect is detected in a frequency range of 5 MHz to 30 MHz, preferably 5 MHz to 15 MHz. Furthermore, the angle wave method or the normal wave method is used in inspecting a depth exceeding 0.5 mm from the surface in which the ultrasonic wave is attenuated inside the material and it is difficult to detect the defect.
Moreover, in the concrete example, when a range of a depth exceeding 0.5 mm from the surface and twice the maximum shear stress depth Z0 (practically a depth of 2 to 3 mm) is inspected, the angle wave method or the normal wave method is used to detect the defect in a frequency range of 5 MHz to 30 MHz, preferably 10 MHz to 25 MHz. When both methods are combined, the above-described problem can be solved.
Additionally, a method for use in detecting the deep range is generally the normal wave method (immersion method), but a position shallower than 0.5 mm is a region (dead band) which cannot be detected by the surface echo to reflect a sonic wave on the surface, and the defect cannot be detected in the normal wave method. To solve the problem, the present inventors have found an optimum method in which the ultrasonic wave is transmitted from the specific surface and a CVT member is highly precisely scanned in order to detect the nonmetal inclusion existing in a surface layer region right under the surface.
It has heretofore been the that a detection limit in ultrasonic inspection is generally a xc2xd wavelength, but according to the method of the present invention, it is possible to detect the defect having a square root length of 0.05 mm in the vicinity of the surface. However, in this case, it is difficult to detect the defect having a target size in a frequency of 5 MHz or less. Moreover, with a frequency exceeding 30 MHz, the sonic wave is largely attenuated, and it is difficult to detect the flaw in the target depth. Therefore, a flaw detection frequency is limited to a range of 5 MHz to 30 MHz. Furthermore, a frequency of 5 MHz to 15 MHz is preferable in a range of 0.5 mm from the surface, and a frequency of 10 MHz to 25 MHz is preferable in a range of 0.5 mm to twice the maximum shear stress depth Z0 (practically a depth of 2 to 3 mm). When the ultrasonic wave of the specific frequency range is selectively used in accordance with the flaw detection depth, a detection intensity having a desired magnitude is maximized. The above-described method is suitable for scanning the portion which undergoes a high bend stress other than the traction surface.
(Action)
The toroidal continuously variable transmission (CVT) is used in an environment having high load and surface pressure, and therefore undergoes a load much larger than the general-purpose rolling bearing. Particularly in the input/output disk, the repeated bend stress is applied to the diagonal-line portion in FIG. 11 (the surfaces 62, 63 and the surface layer portion right under the surfaces), and a high tensile stress is generated. Moreover, similarly in the power roller bearing inner ring, the repeated bend stress is applied to the diagonal-line portion in FIG. 12 (the surfaces 67, 68, 69 and the surface layer portion right under the surfaces), and the high tensile stress is generated. Therefore, the input/output disk and power roller bearing inner ring easily flaking and break starting from these portions.
To prevent the flaking and break, in Prior Document 2, there is disclosed the ultrasonic inspection method which guarantees that large nonmetal inclusions do not exist in the traction surface 62 of the input/output disk and the traction surface 67 and surface layer portion right under the surface of the power roller bearing inner ring. However, in the inspection method of Document 2, the portions shallow from the traction surfaces 62, 67 are objects, and the portions further deeper from the traction surface are not the objects. Moreover, in the inspection method of Document 2, only the surface layer portion right under the traction surface is regarded as the object, and other surface layer portions distant from the traction surface are not the objects.
A main use of the toroidal CVT is a car, but if a damage (flaking or breakage) is enerated in the input/output disk or the power roller bearing, the other components in the CVT mechanism are crucially damaged and a serious accident is possibly caused. Particularly, when the input/output disk or the power roller bearing inner ring breaks during the running of the car, there is a possibility of development of a major accident. Therefore, it is necessary to guarantee quality so that these components are inhibited from breaking.
The present inventors have assumed the repeated bend stress applied to the input/output disk and power roller bearing inner ring in an apparatus with the CVT mounted thereon, and have analyzed a stress distribution generated in the respective members by a finite element method (FEM) using computer graphics simulation. As a result, as shown in FIGS. 13, 14, it has been found that high-stress generated regions 71, 76 exist also in the surface layer portions (one end portion of the inner peripheral surface) of the surfaces 63, 68, 69, 71, 75 other than the traction surfaces 62, 67. That is, as shown in FIG. 13, it has been found that local stress concentration easily occurs in the corner edge 71 with the inner peripheral surface 63 intersecting with the end surface 70 therein and the vicinity of the edge in input/output disks 31, 32. As shown in FIG. 14, it has been found that a local stress is easily generated in the corner edge 76 with the inner peripheral surface 68 intersecting with the end surface 75 therein and the vicinity of the edge in power roller bearing inner rings 36a, 37a. 
Then the present inventors have noted these high-stress generated regions 71, 76, and have intensively researched correlations of size, depth position, and breakage (flaking) of the large nonmetal inclusion included in the surface layer portion. As a result, it has been found that the large nonmetal inclusions having a square root length of 0.2 mm or more are prevented from being included in regions shown by diagonal lines of FIGS. 7 and 8 and the breakage (flaking) can thereby be prevented regardless of any size of the disk and power roller bearing inner ring. That is, the high-stress generated regions 71 of the input/output disks 31, 32 correspond to the portion 61 shown by diagonal lines in FIG. 7, and the high-stress generated regions 76 of the power roller bearing inner rings 36a, 37a correspond to the portion 66 shown by diagonal lines in FIG. 8.
Additionally, the present inventors have confirmed that the flaking or breakage is not generated during a guaranteed life regardless of the sizes of the input/output disk and power roller bearing, as long as the portions of the regions shown by the diagonal lines in FIGS. 7, 8 have a certain constant cleanliness (substantially have no defect).
Here, the xe2x80x9csurface layer portionxe2x80x9d includes not only the portion right under the surface but also the portion in a certain degree of depth from the surface and further the surface.
The present inventors have obtained the maximum shear stress depth Z0 from toroidal CVT design conditions in accordance with the following procedure, have used an obtained Z0 value as a reference to apply various ultrasonic inspections such as the normal wave method, angle wave method, and surface wave method to the input/output disk and power roller bearing inner ring, and have checked the methods. As a result, as shown in Table 3, it has been found that the angle wave method is most suitable for the depth from the surface in a range of once or twice Z0 and that the surface wave method and normal wave methods are most suitable for the depth from the surface in a range of twice or more times Z0.
This Z0 of a time at which the input/output disk and power roller bearing inner ring of the toroidal CVT are rotated and brought into contact, and a method of obtaining Z0 will be described with reference to FIGS. 19 and 20.
Since large repeated shear and bend stresses overlap with each other in a composite manner and act on the input/output disk and power roller bearing of the toroidal CVT, a strict stress load state different from that of a general-use rolling bearing is obtained. The position of the CVT constituting member in which the dynamic maximum shear stress is generated is deeper than that of the general-use rolling bearing.
Here, it is assumed that the depth position on which the dynamic maximum shear stress acts is referred to as the xe2x80x9cmaximum shear stress depth Z0xe2x80x9d. The maximum shear stress depth Z0 is used in calculating a rolling life of each constituting member, when designing the CVT.
The method of obtaining the maximum shear stress depth Z0 will be described using Hertz""s contact theory. When a member 1 elastically contacts a member 2, curvature radii of the members 1, 2 corresponding to a first surface (surface I crossing at right angles in a rotation detection) and a second surface (surface II crossing at right angles in the rotation detection) are represented as xcfx8111, xcfx8112, xcfx8121, xcfx8122. Here, with the application to the contact of a disk (member 1) and power roller (member 2) of a TCVT bearing, the contacts of both the members 1, 2 are given by the following equations (1), (2), (3), (4).
a=(50.5xc3x9710xe2x88x923)xcexcxc2x7(P/xcexa3xcfx81)⅓xe2x80x83xe2x80x83(1)
b=(50.5xc3x9710xe2x88x923)xcexdxc2x7(P/xcexa3xcfx81)⅓xe2x80x83xe2x80x83(2)
b/a={(t2xe2x88x921)(2txe2x88x921)}xc2xd=k1xe2x80x83xe2x80x83(3)
cos xcfx84=|xcfx8111xe2x88x92xcfx8112+xcfx8121xe2x88x92xcfx8122|/xcexa3xcfx81xe2x80x83xe2x80x83(4)
Additionally, symbol a denotes a contact ellipse long axis radius, symbol b denotes a contact ellipse short axis radius, symbol xcfx84 denotes an auxiliary angle, symbols xcexc and xcexd denote constants concerning cost, symbol P denotes a load, and symbol xcexa3xcfx81 (=xcfx8111+xcfx8112+xcfx8121+xcfx8122) denote a sum of main curvatures with which two elastic members form right angles in a contact point.
Moreover, the above-described parameters xcexc, xcexd, k1 have the following relation.
xcexc={2E(k2)/xcfx80k12}⅓
xcexd={2E(k2)k1/xcfx80}⅓
k1=b/a
k2=(1xe2x88x92k12)xc2xd
Therefore, the parameters xcexc, xcexd are constants obtained by second class complete ellipse integration.
The contact ellipse long axis radius a is obtained from the above equation (1), and the contact ellipse short axis radius b is obtained from the above equation (2). These are assigned to the above equation (3) and solved concerning a parameter t, and a dynamic maximum shear stress generated position Zo (depth from the surface) is given by the following equation (5). This is described in pages 230 to 240 of xe2x80x9cBearing Lubrication Manual (Daily Industrial Newspaper Co.; edited by Bearing Lubrication Manual Edition Committee; issued in 1961)xe2x80x9d (hereinafter referred to as Document 5).
Zo=b{(t+1)(2txe2x88x921)xc2xd}xe2x88x921xe2x80x83xe2x80x83(5)
Additionally, the above-described Zo can also be obtained from the relation of the following equation (6) using a maximum contact pressure Pmax.
Pmax=[188xc3x97{P(xcexa3xcfx81)2}⅓]/xcexcxcexdxe2x80x83xe2x80x83(6)
(Calculation Case Example)
Subsequently, the numeric values of the respective parameters are concretely assigned to the above equations (1) to (6), and the maximum shear stress depth Zo and maximum contact pressure Pmax are obtained. Each example of the numeric value of each parameter will be described.
Disk radius ro=40 mm
Power roller radius R22 =32 mm
Contact angle xcfx86=35.4xc2x0 (contact condition of the maximum deceleration time of the CVT)
Load P=52200 N
Power roller rotation center distance D=2r1=130 mm
Coefficient ko={(xcfx86D/2)xe2x88x92ro}/ro=0.625
The above-described numeric values are use to obtain the curvature radii xcfx8111, xcfx8112, xcfx8121, xcfx8122. Additionally, for the values of the xcfx8111, xcfx8112, xcfx8121, xcfx8122, fifth digits after the decimal point are rounded off.
xcfx8111=cos xcfx86/{ro(1+koxe2x88x92cos xcfx86)}=0.0252
xcfx8112=xe2x88x921/ro=xe2x88x920.025
xcfx8121=1/ro=0.025
xcfx8122=1/R22=0.0313
Therefore,
xcexa3xcfx81=xcfx8111+xcfx8112+xcfx8121+xcfx8122=0.0565
|xcfx8111xe2x88x92xcfx8112+xcfx8121xe2x88x92xcfx8122|=0.0439
These numeric values are assigned to the above equation (4) and the value of cost is obtained. Additionally, for the value of cost, the third digit after the decimal point is rounded off.
cos xcfx84=0.0439/0.0565=0.78
An appendix table of Document 5 (ellipse integration table) is used to obtain the parameters xcexc and xcexd corresponding to cos xcfx84=0.78. Additionally, an intermediate value not described in the appendix table of Document 5 was calculated by a proportional calculation method.
xcexc=2.196, xcexd=0.5581
These values of xcexc, xcexd and values of P, xcexa3xcfx81 are assigned to the above equations (1), (2), and a long axis radius a and a short axis radius b of a contact ellipse are obtained.
a=5.05, b=1.283
These numeric values are assigned to the above equation (3), and a solution of a cubic equation (real root) is obtained concerning the parameter t.
t=1.03
The obtained value of t is assigned to the above equation (5) and the maximum shear stress depth Zo is obtained.
xe2x80x83Zo=0.614 (mm)
Furthermore, the respective values of xcexc, xcexd, P, xcexa3xcfx81 are assigned to the above equation (6), and the maximum contact pressure Pmax is obtained.
Pmax=4.05 (GPa)
In the above-described calculation case example, the Zo value is 0.614 mm, and Pmax value is 4.05 GPa.
As described above, according to the present invention, attention is focused on the inspection of the portion in which destruction most easily occurs in the toroidal CVT member, and thereby the quality of the CVT member can be guaranteed with high precision. Particularly when the optimum ultrasonic inspection is used in accordance with the depth from the surface, the inspection precision of the defect is dramatically enhanced, and therefore a level of quality assurance can be raised.
Moreover, according to the present invention, since the defect included in the CVT member is scanned in a nondestructive manner, the total number of CVT members can be inspected, and it is possible to guarantee the quality with the high reliability. Particularly, in the method of the present invention, the true size and shape of the defect can be grasped based on the echo reflected from the defect. Therefore, the high reliability can be obtained as compared with the conventional method of using a microscope to two-dimensionally observe the defect which appears in a cut surface.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.